Deflector arrangement for use in a grinding mill



J. F. DALENBERG ET AL 3,465,971

DEFLEGTOR ARRANGEMENT FOR USE IN A GRINDING MILL Sept. 9, 1969 Filed Dec. 28, 1966 2 Sheets-Sheet 1 JOHN F. PALE/V8526 ELME'E H- TOP? JOHN w. CARPENTER ATTORNEY p 1969 J. F. DALENBERG ETAL 3,465,971

DEFLECTOR ARRANGEMENT FOR USE IN A GRINDING MILL Filed Dec. 28, 1966 2 Sheets-Sheet 2 INVENTORS JOHN F PALE/V5526 ELMEz H- TODD JOHNM CARPENTER By M if A 7'TORNE Y United States Patent US. Cl. 241-53 3 Claims ABSTRACT OF THE DISCLOSURE A pulverizing mill having a rotatable grinding ring and associated grinding rollers, including deflector means positioned above the grinding ring for directing the airborne pulverized material leaving the grinding ring downwardly and inwardly back towards the grinding ring, thus causing the more coarse pulverized particles to separate out and be redeposited on the grinding ring for further pulveriza tion.

This invention relates to an improvement in a rotary bowl mill adapted to grind and pulverize solid materials, and in particular to an improved deflector means for properly guiding the flow of gas and pulverized material within the mill.

In coal and other pulverizing systems, there is always a certain amount of coarse material which is insuificiently pulverized that is conveyed by the gas stream from the grinding elements to the classifier. These coarse particles are separated out in the classifier, and returned to the grinding elements for further grinding action. The heavy recirculation of coarse material is undesirable for a number of reasons. It reduces the efliciency of the mill, since more conveying gas is required to transport these coarse particles from the grinding area to the classifier. Also, friction of these coarse particles against surfaces within the mill causes increased wear and maintenance.

It is an object of this invention to provide deflector means for substantially reducing the amount of coarse material that is carried by the gas stream from the grinding elements to the classifier.

It is a further object to provide deflector means of such a configuration that the coarse particles separated out of the gas stream are evenly distributed beneath the grinding rolls, thereby further increasing the grinding efficiency of the mill.

These and other objects will become more apparent from the following detailed description when considered with the accompanying drawings, wherein:

FIGURE 1 is a sectional side view of a pulverizing bowl mill embodying our invention;

FIGURE 2 is an enlarged plan view of the deflector means shown in FIGURE 1; and

FIGURE 3 is a side view of the deflector means shown in FIGURE 2.

Looking now to FIGURE 1, numeral denotes a bowl mill for grinding coal or other material therein. Inside the housing is positioned a rotatable bowl or table 12, mounted on shaft 14. Shaft 14 along with the attached bowl 12 is rotated by means of worm wheel 18, which engages worm 16 mounted on motor driven shaft 20.

A plurality of grinding elements or rollers 22 are rotatably mounted on shafts 24. An adjustable spring 26 urges each roller 22 towards the upper surface of the grinding ring 12. A material to be pulverized, such as coal, is introduced into the mill through inlet 28. A gas, usually air, enters through opening 30, and flows through annular space 31 to convey the ground material passing over the lip of the bowl upwardly through the mill interior and 3,465,971 Patented Sept. 9, 1969 into the classifier 34. The gas and coal enter the classifier by Way of inlets 32, which contain vane-s for directing the gas tangentially into the classifier. The larger or more coarse particles of coal are separated out of the gas stream by centrifugal force, and fall back onto the grinding ring 12 through bottom opening 36 for further grinding. The finer particles of coal are carried along with the gas stream and leave the mill through outlets 38.

Positioned in annular space 31 are a plurality of blockoff plates 42, there being one such blockoif plate for each roller 22. Each block-oif plate 42 is positioned directly below its associated roller 22, and prevents pulverized coal from being carried upwardly into the area of the shafts the rollers are mounted on, which could impede their operation, and also could cause undue wear of these parts.

Positioned in the open annular spaces 31 adjacent to block-oif plates 42 are a plurality of directing vanes 44, which guide the gas and coal particles away from the plates 42, and into the space beneath the deflector means 40. These directing vanes 44 cause substantially all of the gas and coal particles to flow into the space beneath the deflector means 40.

Looking now to FIGURES 2 and 3, one of the deflector means is shown in more detail. The deflector means 40 has an upper triangular shaped portion 48, a streamlined portion 52, and a side portion 50. Strut member 46 and angle iron 55 connect the deflector means 40 to the mill housing, and form the support for the deflector. Streamlined portion 52 of the deflector 40 has a planar lower edge 54 which is slightly spaced from, and is parallel to, the upper surface of the grinding ring 12.

The operation of the mill will now be described. Coal to be pulverized enters the mill through inlet 28. After being pulverized between the upper surface of grinding ring 12 and rollers 22, the pulverized coal particles are thrown outwardly by centrifugal force into annular space 31. Gas flowing through directing vanes 44 in annular space 31, picks up the pulverized particles, and the gas-solid stream is guided by side wall 50 to the streamlined portion 52 and triangular portion 48 of the deflector means 40.

When the gas-solid stream reaches edge 54, it makes a sharp turn, and flows upwardly towards the classifier 34. As the gas-solid stream makes the sharp turn at edge 54, the finer solid particles, having little inertia, are carried along with it. The coarser or larger particles, having more inertia, tend to drop out of the gas stream at this point, back onto the grinding ring 12.

The as along with only fine particles entrained enters classifier 34 by way of inlets 32. The remaining few oversize, heavy particles Will be separated out of the stream by centrifugal force in the classifier 34, and fall back onto grinding ring 12 by way of opening 36. The fine particles will be carried along with the gas stream out of the mill through outlets 38.

Both the coarse particles separated out of the stream by deflectors 40, and the coarse particles separated out by classifier 34, will be fed beneath the grinding rolls 22 in a level, uniform manner by the overhanging edge 54 of the deflector means. As the bowl 12 rotates, the coal particles carried thereby will be spread across the bowl by the edge 54 into a bed of material to be pulverized which is of uniform depth. This prevents uneven piling up of material against the rolls, which piling up increases the energy required to turn the rolls because of friction, and particle deformation to a size less than necessary and also reduces the grinding efficiency of such rolls.

From the above, it can be seen that the deflector means 40 by separating out a substantial portion of the heavy particles, will result in a number of advantages. It reduces the energy requirements of the mill while increasing its tributed along the length of the rolls by the overhanging edge of the deflector means.

While we have illustrated and described the preferred embodiment of our invention, it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. We therefore do not Wish to be limited to the precise details set forth but desire to avail ourselves of such changes as fall Within the purview of our invention.

What we claim is:

1. A pulverizing mill comprising a closed casing, a grinding ring mounted within the casing for rotation about a central vertical axis, means for supporting and rotating the grinding ring, at least one grinding element mounted to coact with the grinding ring, means for introducing material to be pulverized onto the grinding ring, there being an annular gas passage between the grinding ring and the enclosing Wall of the casing, means for forcing gas upwardly through this annular passage to carry away pulverized particles in suspension, at least one of deflector means positioned above the annular passage, said deflector means being such in number and of such configuration that they direct a majority of the gas along with the pulverized particles both inwardly and downwardly, thus causing the more coarse pulverized particles to separate out of the gas stream and to be redeposited on the grinding ring.

2. A pulverizing mill comprising a closed casing, a grinding ring mounted within the casing for rotation about a central vertical axis, means for supporting and rotating the grinding ring at least one grinding roller mounted to coact with the grinding ring, means for introducing material to be pulverized onto the grinding ring, there being an annular gas passage between the grinding ring and the enclosing wall of the casing, means for forcing gas upwardly through this annular passage to carry away pulverized particles in suspension, at least one deflector means positioned above the annular passage, a plurality of guide vanes positioned so as to direct a majority of the gas along with the pulverized particles into the deflector means, each deflector means having a curved surface which is directed downwardly and inwardly towards the grinding ring, the edge of such surface being spaced from the grind ing ring, whereby the gas along with the pulverized particles entering the deflector means is directed inwardly and downwardly by the deflector means, thus causing the more coarse pulverized particles to separate out of the gas stream and be redeposited on the grinding ring, Whereas the gas and fine pulverized particles flowing past the edge of the surface of the deflector means reverses its direction and continues to flow upwardly.

3. The pulverizing mill set forth in claim 2, wherein there is one deflector means associated with each grinding roller, each deflector means being positioned upstream of its associated grinding roller in the direction of rotation of the grinding ring, the edge of the curved surface of each deflector means is parallel to the upper surface of the grinding ring, and extends in a radial direction sufficient to cause the material being pulverized to be fed evenly throughout the length of each grinding roller.

References Cited UNITED STATES PATENTS 2,206,145 7/1940 Wood 241-53 2,431,746 12/1947 Frangquist 241-53 2,641,387 6/1953 Christensen 241-119 X 2,698,142 12/1954 Crites 241-53 2,818,219 12/1957 Straight 241-119 ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner U.S. Cl. X.R. 241-119, 220 

